The purpose of this study is to assess the effects of carotid endarterectomy (CE) and extracranial-intracranial bypass(EIAB) on neuropsychological functioning of patients with transient cerebral ischemia and progressive or completed cerebral infarction. A neurobehavioral battery including psychological tests, neurological data, and behavioral sampling, will be employed to assess patients preoperatively and postoperatively over eighteen months. The results of neuropsychologival assessment will be correlated with data from serial angiography and Doppler sonography. Medical and neuropsychological results will be studied for their relationship to demographic or health history factors. A review of the literature suggests a tendency to confound the two purported benefit of cerbral revascularization: (1) improvement of neurological and neuropsychological deficits and (2) prevention of future ischemic episodes. The primary goal of the proposed study is to delineate, compare, and predict the effectiveness of EIAB and CE in reversing neuropsychological deficits and in improving overall activity level and quality of life. In accordance with suggestions made during the previous review, we revised our research plan to (1) reduce practice effects; (2) specify summary measures; (3) obtain auditory, visual, and somosensory evoked responses as additional criterion measures; and (4) include retrograde amnesia measures. As an additional comparison group, we have expanded our sample to include nonoperated subjects with symptoms of focal cerebral ischemia. We also present new supporting data to demonstrate the feasibility of our study.